1. Field of the Invention
This invention relates to polymer dispersions and their uses. The dispersions are prepared by the in situ polymerization of an ethylenically unsaturated monomer in a chain extender in the presence of a free radical polymerization initiator and a polyamide having a pendent amide group. They are used to blend with active hydrogen-containing compounds to prepare polyurethane products.
2. Description of the Prior Art
One of the challenges faced by those working to improve products made from polyurethane polymers is to develop products which have acceptable mechanical properties, but which can be easily processed.
It is known that the mechanical properties of polyurethane products can be improved by the use of graft polymer dispersions such as those described in U.S. Pat. No. Re. 28,715 and U.S. Pat. No. 29,014. It is also known that the mechanical properties of polyurethane elastomers can be improved if chain extenders such as low molecular weight diols are added to the formulation. The chain extender is usually added to the graft polymer dispersion before reacting with the organic polyisocyanate. The problem with this approach is that the chain extender is often not compatible with the polyol and results in phase separation of the graft polymer dispersion and chain extender. Moreover, the resulting compositions often have an unacceptable viscosity which makes processing difficult.